This invention relates to powered wheelchairs. More particularly, the present invention concerns a powered wheelchair having an independent suspension and an adjustable center of gravity.
Power drive wheelchairs in general are known in the art to provide motorized mobility to persons confined to a wheelchair. Such power drive wheelchairs conventionally comprise a relatively sturdy wheelchair frame supported on wheels for rolling movement, in combination with one or more batteries for supplying electrical power to one or more electrical motors coupled to the drive wheels of the wheelchair. An electronic control unit is also carried by the wheelchair to regulate power driven operation of the drive motor or motors. This is typically done in accordance with the positioning of a joystick-type control mechanism. Such joystick controls are usually located in close proximity to an armrest of the wheelchair. In many modern power drive wheelchairs, the control unit utilizes pulse width modulation techniques to regulate a pair of separate drive motors in a manner permitting sample joystick selection of wheelchair drive direction and speed. The wheelchair frame further carries a seat module including a seat and a backrest as well as armrests.
One of the problems associated with powered wheelchairs is that they have a tendency to tip backwards upon initial acceleration. The torque generated by the motor is often substantial and the unwary user may tip the wheelchair over. In light of this problem, many wheelchair manufacturers now provide anti-tip caster wheels positioned rearward of the drive wheels and mounted at a level just above the ground. As the wheelchair begins to tip backward, the anti-tip caster wheels engage the ground to prevent further tipping. However, such caster wheels are usually mounted on arms that are rigidly coupled to the support frame.
While such anti-tip mechanisms successfully prevent rearward tipping of the wheelchair in most instances, the rigid coupling of the anti-tip wheel to the support frame provides a fairly sudden jolt to the wheelchair's occupant as the anti-tip wheels engage the ground. Contact of the anti-tip wheel with the ground shifts the momentum of the wheelchair's occupant from a rearward direction to a forward direction thereby jolting the occupant. Such jolting is obviously undesirable for the occupant of the chair. Jolts are also encountered by the chair's occupant as the motorized chair moves over uneven floor or ground surfaces, such as cracks in concrete, curbs, or even simply a movement from a carpeted area to a bare floor area.
Another problem with conventional powered wheelchairs is that the vibrations of the motor are not isolated from the occupant of the wheelchair. As with jolts, motor vibrations also disturb the occupant of the wheelchair.
A further problem with powered wheelchairs has been the lack of adjustability of the seat module section of the chair. While adjustable seats and seatbacks are offered in manually powered chairs, this option has not been available in power drive wheelchairs despite the fact that such an option would be particularly advantageous to users of same.
Still a further problem with conventional powered wheelchairs has been that such wheelchairs are not provided with adjustable centers of gravity. This feature would be advantageous in order to allow the chair to be customized for the needs of the particular type of user employing the chair. For example, if the rear or power drive wheels of the chair could be brought more directly underneath the seat, thereby reducing the amount of downward force exerted on the front casters of the wheelchair, this would improve the maneuverability of the wheelchair making it easier to use in confined spaces. Alternatively, if the power drive wheels of the chair can be spaced further away from the seat, this would enlarge the wheel base of the chair, thereby making it more stable and less likely to tip.
Accordingly, it has been considered desirable to develop a new and improved powered wheelchair which would overcome the foregoing difficulties and others while providing better and more advantageous overall results.